Israel’s treatment of civilians in Gaza poses a deepening dilemma for the Biden administration, as officials scramble to illustrate strong support for a core U.S. ally following Hamas’ brutal assault while grappling with a spiraling human toll that could threaten Israel’s international backing and undermine America’s own steps to shield noncombatants from harm.

The plight of civilians is drawing intense global scrutiny ahead of President Biden’s planned Wednesday visit to Israel, where the U.S. leader will underscore his backing for America’s closest Middle Eastern partner, still reeling from the devastating surprise attack that killed at least 1,400 people near the country’s border with the Gaza Strip.

Palestinian authorities said at least 500 people were killed in a strike on a crowded hospital in Gaza City on Tuesday, adding a dramatic escalation to a death toll that already stood above 2,000 since Israeli forces began pounding the densely populated area with airstrikes following Hamas’ Oct. 7 assault. As many as 1 million people were ordered to flee south as bombardment reduces much of northern Gaza to rubble and conditions deteriorate following Israel’s suspension of water and electricity to the Hamas-ruled enclave, posing an additional test for Biden as he flies to the Middle East.

Biden, in a statement issued as he travels to Israel, said he was “outraged” by the hospital explosion. The United States, he said, “stands unequivocally for the protection of civilian life during conflict.” In turn, Palestinian Authority President Mahmoud Abbas canceled his planned meeting with Biden, and a summit that was to include Biden and the leaders of Egypt and Jordan also was called off.

The potential for far greater casualties during Israel’s expected ground offensive against Hamas will likely intensify the challenges that Biden, who has positioned his administration as a chief defender of global norms amid what U.S. officials characterize as Russia’s illegal and immoral attacks on civilians in Ukraine, must navigate in his show of solidarity with Israel.

Prime Minister Benjamin Netanyahu has vowed to “demolish” Hamas as Israel comes together to prevent further attacks.

But Kenneth Pollack, a Middle East expert at the American Enterprise Institute, said Israel risks repeating the missteps America made in the wake of 9/11, when a shaken nation embraced a broad military and intelligence response that ultimately alienated many early supporters and inspired a new generation of anti-American sentiment worldwide.

“This is the delicate tightrope the Biden administration has to walk. They’ve got to deal with people who are just like us 22 year ago,” Pollack said. “They’ve got to be simultaneously sympathetic with the Israelis . . . and give them the benefit of the wisdom of our mistakes.”

Since the outset of the conflict, the Biden administration has declared the protection of civilian life and humanitarian assistance a priority even as it refrains from criticizing Israeli tactics. Administration officials including Secretary of State Antony Blinken have pressed Israeli leaders in recent days, with mixed results, to embrace steps they hope will minimize civilian suffering, focusing their pleas on facilitating the entry of aid into Gaza.

Biden himself, a longtime supporter of Israel who has issued an emotional condemnation of Hamas’ “act of sheer evil,” has pledged unqualified support for Israel’s goal of obliterating the group. But the president and his aides, facing pressure from within the Democratic Party to curb the violence, also are warning Israel against reoccupying Gaza and saying they expect Israel to adhere to the laws of war.

The crisis complicates an ongoing Biden administration effort to develop far-reaching safeguards to prevent civilian deaths in wartime, an issue that dogged the United States during two decades of counterinsurgent wars. While the Pentagon conceded at least 1,300 civilian deaths in operations against the Islamic State in Iraq and Syria, for example, watchdogs say the true toll is likely far higher.

“You have an administration that has made very public commitments to improve how it addresses civilian harm, including with partners,” said Annie Shiel, U.S. advocacy director at the Center for Civilians in Conflict. “And if the U.S. isn’t going to be firm with Israel about civilian harm and its obligations, then those commitments seem like they go out the window.”

Last year, the Biden administration stood up a first-of-its-kind initiative to prevent, track and respond to civilian casualties caused by U.S. military operations. Biden also approved new guidelines for arms transfers that elevate the role of human rights and international humanitarian law in approving such transactions. More recently, the State Department established a first-of-its-kind process for responding to suspected incidents in which allied countries have used U.S.-made weapons against civilians.

Legal experts said that expanding U.S. military support for Israel meanwhile carries with it weighty considerations for the United States as reported Palestinian casualties mount. Already the administration has positioned two aircraft carriers in the eastern Mediterranean, dispatched an amphibious task force to the area, and expedited shipments of munitions and air defense missiles. How Israel employs U.S.-origin weapons, experts said, may now have new implications for the United States.

Israel has long been the top recipient of annual U.S. military aid, receiving more than $3 billion a year.

Brian Finucane, who served as a State Department attorney during the Obama administration, said the considerations include domestic laws governing arms sales specifying that U.S. weapons can be sold to other countries for the goal of “legitimate self-defense” and international laws that could, in theory, implicate a donor of military aid to a nation that then goes on to violate the laws of war with those arms.

That issue echoes the internal debates that occurred during the height of the war in Yemen, when some U.S. officials warned that American military support to Saudi Arabia could implicate the United States in repeated Saudi strikes on Yemeni civilians.

While U.S. officials have publicly voiced confidence that Israel will conduct a responsible campaign, strikes like the one that hit the al-Ahli Hospital in central Gaza City on Tuesday should “at a minimum prompt hard questions” from officials involved in approving arms sales, Finucane said. Israeli authorities blamed the attack on a Palestinian militant group.

“It’s deeply problematic to simply assume that a foreign partner will comply with a law of war and that all civilian deaths will be incidental,” said Finucane, who is now a senior adviser at the International Crisis Group.

The situation could also create broader diplomatic challenges for Washington as it seeks to marshal global support for Israel. While major powers like Russia and China have already criticized Israeli tactics and called for a cease-fire, European leaders have so far sought to illustrate their solidarity.

But even they face challenges in navigating the conflict’s global context, as demonstrated by the backlash that European Commission President Ursula von der Leyen faced after she expressed full solidarity for Israel on Friday without also mentioning civilian casualties in Gaza. European diplomats privately worried that she risked undermining global support for Europe’s efforts to help Ukraine by seeming to turn a blind eye to the deaths of Palestinian civilians while highlighting Russia’s attacks on Ukrainians. The United Nations has cautioned that Israel’s siege of the enclave and its evacuation order could violate international law.

The administration’s struggle to secure measures benefiting civilians reveals the limits of U.S. influence at a moment of intense regional crisis. In the opening days of the war, the Biden administration’s first humanitarian initiative was to negotiate the safe passage of Palestinian civilians from Gaza to Egypt through the Rafah border.

The administration quickly abandoned that plan after consultations with Arab partners who opposed the proposal out fear that fleeing Palestinians may never be able to return to Gaza - a major hang-up given the painful history of generations of Palestinian refugees.

“I’ve heard directly from Palestinian Authority President Abbas and from virtually every other leader that I’ve talked to in the region, that that idea is a nonstarter,” Blinken told al-Arabiya on Sunday. “We believe that people should be able to stay in Gaza, their home.”

As a result, the Biden administration switched tactics and embraced the idea of establishing “safe zones” inside Gaza. “Our focus now is on helping to create safe zones,” Blinken, in the midst of a marathon regional tour, told reporters in Qatar. “We’re doing that with the leading international organizations.”

Thus far, the U.S. plan for safe zones has yet to materialize.

Despite a bargaining session between Blinken and Israel’s war cabinet that went for more than seven hours from Monday evening into the early hours of Tuesday morning, the two sides were only able to agree “to develop a plan” that will include the “possibility of creating areas to help keep civilians out of harm’s way,” Blinken said after emerging from the meeting.

The announcement included no timeline for when this would be established or any details about how such safe zones might work in a densely populated territory where civilians and militants are nestled in tightly together. Another message that Arab leaders underscored was that a humanitarian collapse in Gaza would enrage the Muslim world and potentially destabilize their own populations.

Those sentiments drove U.S. officials to prioritize the shipment of aid into Gaza in discussions with Israel’s war cabinet - a humanitarian challenge that took up more time than any other topic in the meeting, according to a State Department official who spoke on the condition of anonymity to discuss a sensitive issue.

Even then, however, the two sides only agreed that they continue to work on a plan “that will enable humanitarian aid from donor nations and multilateral organizations to reach civilians in Gaza,” Blinken said.

While Blinken’s discussions with Arab leaders helped move the Biden administration away from a focus on moving Palestinians out of Gaza - and toward safe zone - the two sides continue to disagree on the issue of de-escalation.

During Blinken’s meeting with Crown Prince Mohammed bin Salman, the Saudi leader “stressed” the need to stop the military operations “that claimed the lives of innocent people” - a reference to Israel’s offensive - and lift the “siege of Gaza,” according to the Saudi summary of the meeting.

The crown prince also called for a halt in the “current escalation” in the conflict.

During Blinken’s meeting in Cairo with Abdel Fatah El-Sisi, the Egyptian strongman said Israel’s assaults have exceeded “the right of self-defense,” and turned into “collective punishment.”

By contrast, a leaked State Department memo, confirmed by The Washington Post, warned U.S. diplomats from using the phrases “de-escalation/ceasefire,” “end to violence/bloodshed” and “restoring calm” as the words do not comport with current U.S. policy.

U.S. officials continue to insist that Israel be allowed to wage an operation that will eradicate Hamas, even as security experts worry that the bombing campaign, involving thousands of bombs, has already had a devastating toll on civilians.

Hudson reported from Amman, Jordan. Michael Birnbaum in Washington contributed to this report.